1. Field of the Invention
The present invention relates to a liquid crystal display panel preferable for use for displaying various kinds of information; an image display apparatus; a method for driving an image display apparatus; and a terminal apparatus.
2. Description of the Related Art
Currently, image display apparatuses carrying liquid crystal display panels are widely used in liquid crystal televisions, displays for personal computers, portable electronic devices, and the like.
As methods for applying an electric field to the liquid crystal layer of a liquid crystal display panel, methods in longitudinal electric field modes and lateral electric field modes are known. In liquid crystal display panels in the longitudinal electric field modes, an electric field in a generally longitudinal direction is applied to liquid crystal molecules by a pair of electrodes disposed across a liquid crystal layer. As such liquid crystal display panels in the longitudinal electric field modes, those in a TN (Twisted Nematic) mode, a VA (Vertical Alignment) mode, a MVA (Multi-domain Vertical Alignment) mode, and the like are known. In the liquid crystal display panels in the lateral electric field modes, a pair of control electrodes was disposed, to be insulated from each other, on the inner surface side of one of a pair of substrates disposed across a liquid crystal layer, and an electric field in a generally lateral direction is applied to liquid crystal molecules. As such liquid crystal display panels in the lateral electric field modes, those in an IPS (In-Plane Switching) mode in which a pair of electrodes does not overlap in two-dimensional view and in a FFS mode in which a pair of electrodes overlaps in two-dimensional view are known.
As illustrated in FIG. 37, in the liquid crystal display panel in the IPS mode, a pair of electrodes including pixel and common electrodes is formed in a comb shape to be engaged in the state of being electrically insulated from each other and an electric field is applied to a liquid crystal in a lateral direction between the pixel and common electrodes. The electric field in the lateral direction causes to liquid crystal molecules to rotate in an in-plane direction to enable the adjustment of the amount of transmitted light. The liquid crystal display panel in the IPS mode has the advantage of having a wider viewing angle than that of the liquid crystal display panel in the longitudinal electric field mode.
In the liquid crystal display panel in the IPS mode, a lateral electric field is generated between comb electrodes and a longitudinal electric field is generated on the comb electrodes. As a result, since lateral electric field components become small on the comb electrodes, it is impossible to sufficiently rotate liquid crystal molecules and transmittance on the electrodes is decreased. Further, it is known that the way of applying an electric field is changed on the ends of the comb electrodes, a domain in the state of orientation of the liquid crystal molecules that are normally rotated and a domain in the state of being rotated in the reverse direction (reverse rotation domain) are therefore generated, and a region having poor orientation called disclination is generated in the boundary between both domains. The boundary between the domains becomes the factor of deterioration of display quality or reliability because of having low transmittance and being in an unstable orientation state. Against such a problem, a comb electrode structure in which the electric field on the electrode ends is controlled to stabilize the reverse rotation domain is proposed (Japanese Patent Laid-Open No. 10-026767 (U.S. Pat. No. 2,973,934) (Patent Literature 1)).
In the liquid crystal display panel in the FFS mode, a pair of electrodes including common and pixel electrodes is disposed on different layers via an insulating film, a slit-shaped opening is formed in the common or pixel electrode on a liquid crystal layer side, and a fringe electric field is applied to the liquid crystal layer through the slit-shaped opening. The liquid crystal display panel in the FFS mode has been often used in recent years because of having the effect of being able to obtain a wide viewing angle and being able to improve its transmittance to improve image contrast. Examples of the known the liquid crystal display panel in the FFS mode are: a liquid crystal display panel in which common and pixel electrodes are formed on substantially the same plane as that of a thin film transistor TFT (Thin Film Transistor) as a switching element; and a liquid crystal display panel in which both common and pixel electrodes are disposed above TFT.
As illustrated in FIG. 38, in the liquid crystal display panel in the FFS mode in which both common and pixel electrodes are disposed above TFT, the surface of TFT or the like is coated with an interlayer resin film, and a lower-layer electrode (herein referred to as a first control electrode) and an upper-layer electrode having a slit-shaped opening (herein referred to as a second control electrode) are formed on the surface of the interlaminar resin film. The upper-layer and lower-layer electrodes are composed across an inter-electrode insulating film, and both electrodes include transparent electrodes. Both of the upper-layer and lower-layer electrodes can be operated as any of pixel and common electrodes.
Such a reverse rotation domain as mentioned above is also generated in the FFS mode. Further, the FFS mode has a problem that an electric field generated from one electrode in a subpixel influences an adjacent subpixel to unnecessarily move liquid crystal molecules in the adjacent subpixel.
As illustrated in FIG. 38, a pixel structure in which the number of slits is reduced to reduce the influence of the reverse rotation domain and a spacing between the slits of subpixels adjacent to each other is increased to suppress the influence of an electric field from an adjacent pixel is proposed (Japanese Patent Laid-Open No. 2007-248999 (Patent Literature 2)).
In recent years, mobile phones and information terminals carrying liquid crystal display panels in such a lateral electric field mode have been widely used, and the miniaturization and higher definition of image display apparatuses have proceeded with the advance of mobile phones and information terminals.
On the other hand, an image display apparatus that enables an observer to observe a different image depending on an observation position, i.e., an image display apparatus capable of observing different respective images from a plurality of eyepoints; and a three-dimensional image display apparatus that enables an observer to three-dimensionally observe images that are each different, as parallax images, have received attention as image display apparatuses having new added value.
As the mode of providing the different respective images to the plural eyepoints, there has been known the mode of synthesizing image data for respective eyepoints to display the data on a display panel, separating the displayed synthetic image by optical separation means including a lens or a barrier (light shielding plate) having slits, and providing images to the respective eyepoints. The principle of the image separation is based on limitation of visible pixels in each eyepoint direction by using the optical means such as a barrier having slits or a lens. As the image separation means, there is generally used a parallax barrier including barriers having a large number of banded slits or a lenticular lens in which cylindrical lenses unidirectionally having a lens effect are arranged.
The three-dimensional image display apparatus employing the optical image separation means is suitable for being carried by a terminal apparatus such as a mobile phone in terms of eliminating the need for wearing special glasses and saving the inconvenience of wearing glasses. A mobile phone carrying the three-dimensional image display apparatus including the liquid crystal display panel and the parallax barrier has been already commercialized (for example, see Nikkei Electronics, Jan. 6, 2003, No. 838, pp. 26-27 (Non Patent Literature 1)).
However, in the above-described mode, i.e., in the three-dimensional image display apparatus which provides the different respective images to the plural eyepoints using the optical separation means, a boundary between images may look dark when the eyepoint position of the observer moves to change an image to be observed. The boundary between the images changed due to each eyepoint is referred to as an optical principal axis of the image separation means. Decrease in luminance occurring in the optical principal axis is caused by observing non-display regions (light shielding sections generally referred to as black matrices in the liquid crystal display panel) between pixels for the respective eyepoints. The above-described phenomenon caused by the movement of the eyepoint of the observer does not occur in general three-dimensional image display apparatuses without any optical separation means. Therefore, the observer feels a sense of incongruity or deterioration in display quality in the above-described phenomenon occurring in the multi-view three-dimensional image display apparatus or the three-dimensional image display apparatus including the optical separation means.
This luminance fluctuation is a phenomenon generally called 3D moire. The 3D moire is the periodic unevenness of luminance (also may be referred to as color unevenness) caused by displaying different images in different angular directions. Further, the 3D moire is a luminance angular fluctuation, and three-dimensional vision is unfavorably affected when the luminance angular fluctuation is high.
In general, a fringe pattern generated by interference of structures each having different periodicities is referred to as a “moire fringe”. Since the moire fringe is an interference fringe generated depending on the periodicity or pitch of a structure while the 3D moire is luminance unevenness occurring due to the image formation property of image separation means, the moire fringe and the 3D moire are distinguished from each other and applied in the present specification.
In order to solve the above-described problems caused by the optical separation means and the light shielding section, three-dimensional image display apparatuses prepared by devising the shapes and arrangement of pixel electrodes and light shielding sections in display panels to suppress deterioration in display quality are proposed (e.g., Japanese Patent Laid-Open No. 2005-208567 (U.S. Pat. No. 4,371,012) (Patent Literature 3) and Japanese Patent Laid-Open No. 10-186294 (U.S. Pat. No. 3,525,995) (Patent Literature 4)).
FIG. 39 is a plan view that illustrates a display panel in a display apparatus disclosed in Japanese Patent Laid-Open No. 2005-208567 (U.S. Pat. No. 4,371,012) (Patent Literature 3). In the display panel illustrated in FIG. 39, the proportion of light shielding sections (wiring lines 1070 and light shielding sections 1076) to openings is substantially constant, when the cross section of the display panel is presumed in a longitudinal direction 1011 perpendicular to the direction of arranging cylindrical lenses 1003a, at any point in a lateral direction 1012. FIG. 39(A) illustrates an example in which a subpixel has a trapezoid shape while FIG. 39(B) illustrates an example in which a subpixel has a parallelogram shape.
In the display panel illustrated in FIG. 39, the proportion of light shielding sections to be observed is substantially constant even when an observer moves an eyepoint in the lateral direction 1012 which is the direction of separating an image to change an observation direction. In other words, the observer does not observe only light shielding sections from a specific direction and display does not look dark. Thus, deterioration in display quality caused by a light shielding region can be prevented.
The display panel illustrated in FIG. 39(B) is a liquid crystal display panel in a lateral electric field mode to which an IPS mode is applied. Each subpixel is formed in a parallelogram shape, and a comb electrode pair disposed on each subpixel tilts toward a direction different from the longitudinal direction 1011 and is disposed along the oblique side of the parallelogram. The direction of the oblique side of the parallelogram is changed every one line, and the oblique side becomes a meandering oblique side which meanders in the longitudinal direction 1011. The comb electrodes are disposed in their drawing directions that are mutually different between subpixels adjacent to each other in the longitudinal direction 1011.
FIG. 40 is a view that schematically illustrates pixels in a three-dimensional image display apparatus disclosed in Japanese Patent Laid-Open No. 10-186294 (U.S. Pat. No. 3,525,995) (Patent Literature 4). FIG. 40(A) is a plan view that illustrates pixel arrangement in the three-dimensional image display apparatus described in Japanese Patent Laid-Open No. 10-186294 (U.S. Pat. No. 3,525,995) (Patent Literature 4) while FIG. 40(B) is an enlarged view of the pixels. The three-dimensional image display apparatus disclosed in Japanese Patent Laid-Open No. 10-186294 (U.S. Pat. No. 3,525,995) (Patent Literature 4) continuously provides substantially uniform luminance in a horizontal direction and is capable of maintaining substantially constant luminance over the whole since the total size of pixels adjacent over an overlapping region 1013 in a vertical direction is constant and is equal to the size of a rectangular region B in a vertical direction. Accordingly, luminance in the case in which the eyes of an observer cross the boundary between subpixels can be therefore maintained at a constant level when the same image is output to adjacent pixel columns.
In Japanese Patent Laid-Open No. 2005-208567 (U.S. Pat. No. 4,371,012) (Patent Literature 3) or Japanese Patent Laid-Open No. 10-186294 (U.S. Pat. No. 3,525,995) (Patent Literature 4), the width of the pixel overlapping region becomes a crosstalk region in which light emitted from a pixel 4R for the left eye and light emitted from a pixel 4L for the right eye overlap each other without being able to be separated by optical means. In the pixel structures in the related art, it is necessary to form at least the crosstalk region in order to set an opening width in the longitudinal direction 1011 at a constant level in an X direction and, as a result, the leakage of the image of one of the right and left eyes to the other, called a 3D crosstalk during three-dimensional display, occurs. Since there is a potential for the 3D crosstalk to result in less of three-dimensional feeling and to exert an influence such as eye fatigue on an observer at the increased value thereof, it is desirable to set the amount of the 3D crosstalk at a predetermined level or less.